The present invention is directed to a device for connecting two webs of material during a flying roll change. A connecting device is used to connect the two webs and a cutting device is used to cut the exhausting web from its roll once the webs have been connected.
A device for accomplishing a flying roll change is known from DE 42 18 825 A1. A fresh paper web can be glued to the paper web which is running-out in a printing press operating at production speed. After the fresh paper web has been glued on, the paper web which is running-out is cut by use of a cutting device and two web ends are formed in the process. The one web end, together with the fresh paper web, is conveyed through the printing press, and the second web end, together with the used up paper roll, can be removed from the roll changer. In the course of the roll change, both paper rolls rotate in the same direction, and the running-out paper web is moved past the fresh paper roll in such a way that, in the course of gluing it to the running-out paper web, the start of the fresh paper web is brought into contact with the running-out paper web in as tangentially a way as possible.
Another device for accomplishing a flying roll change is known from U.S. Pat No. 4,936,942, wherein a cutting device and a gluing roller are provided in a frame. For a roll change, the frame can approach the running-out paper web from one side, so that when the connecting device is triggered, a gluing roller, together with the running-out paper web, is pressed against a gluing spot of the fresh paper web. Thereafter, the running-out paper web is cut by the cutting knife.
Yet another device for accomplishing a flying roll change is known from EP 0 720 581 B1. The tension of the paper web can be kept substantially constant during the gluing or cutting process by a suitable kinematic movement process.
In connection with the generally known devices for connecting two paper webs in the course of a flying roll change, it is disadvantageous that, because of the arrangement of the connecting device, for example a gluing roller or gluing brush, downstream of the cutting device, in the feed direction of the running-out web of material, a so-called xe2x80x9cslipxe2x80x9d is necessarily formed. In this case, the length of this slip, i.e. the distance between the connecting point of the fresh and the old web of material and the cut-through web end of the old web of material, is essentially determined by the distance between the connecting device and the cutting device. Interferences are often caused by the slip in the course of conveying the web of material through a processing machine, for example a web-fed rotary printing press. To prevent these interferences, a device is proposed in WO 99/40004 A1, wherein, by use of an appropriate web guidance after the cutting of the old web of material, the slip is pushed outwardly by the centrifugal forces acting on the slip and is subsequently cut off by a cutter bar. It is possible with this to shorten the length of the slip to almost zero. However, a considerable additional structural outlay is required for an appropriate web guidance and for the downstream connected cutter bar.
The object of the present invention, is directed to providing a device for connecting two webs of material.
In accordance with the present invention, this object is attained by connecting the two webs of material, each wound on a separate roll, during a flying roll change. A connecting device is provided for connecting the fresh web of material with the exhausting web of material. A cutting device is used to cut the exhausting web once the connection has been made. The cutting device and the exhausting web, which is to be cut, are brought into engagement by changing the course of travel of the web to be cut.
The advantages to be obtained by the present invention lie, in particular, in that, because of the arrangement of the cutting device downstream of the connecting device, viewed in the feeding direction of the running-out web of material, the slip can be basically cut off as short as desired when the running-out web of material is cut. When connecting the fresh web of material to the running-out web of material, the result always is a Y-shaped structure, one of whose branches, namely the old web of material starting at the old roll of material up to the gluing point, can essentially be completely cut off by the cutting device which is arranged downstream of the connecting device. By arranging the cutting device downstream of the connecting device, no minimum slip length necessarily results, but the length of the slip can basically be shortened as desired. However, in the course of this, it should be noted that, if the slip length is selected to be too short, there is the potential danger that the fresh web of material is inadvertently damaged by the cutting device.
If the cutting device is arranged downstream of the connecting device, there is the potential danger that the fresh web of material is also inadvertently damaged in the course of cutting through the old web of material. To reliably prevent this danger, it is particularly advantageous if the cutting device is brought into engagement with the web of material to be cut by moving a web guide device, by which the course of the web of material to be cut can be changed. As a result, it is possible to accomplish that the fresh web of material and the web of material to be cut off are guided along different paths in the area downstream of the gluing point, so that only the old web of material is cut. By moving the web guide device, it is, in particular, possible for the fresh web of material and the web of material to be cut to form a defined angle with respect to each other. In this case, the cutting device for cutting the old web of material must be arranged in such a way that, after the gluing point has passed the cutting device, because of its course the old web of material can be cut by contact with the cutting edge of the cutting device. An advantage of this configuration resides, in particular, in that the cutting device for cutting the old web of material need not be moved, but can be arranged fixed in one place.
The change of the course of the old web of material, which is required for cutting the old web of material, can be achieved in a particularly simple manner. The connecting device, for example a gluing roller or gluing brush, after it has pressed the running-out web of material against the fresh web of material, is displaced in such a way that the old web of material comes into engagement with the cutting device.
Alternatively to the displacement of a web guide device, by which the course of the web of material to be cut can be altered, it is also possible that the cutting device will come into engagement with the web of material to be cut by use of a suitable displacement of a web guide device, by which the course of the fresh web of material can be changed, and which will accomplish the simultaneous change of position of the cutting device. In other words, this means that by changing the web guide device, the fresh web of material is rerouted, at least briefly, in such a way that after the position of the cutting device has been changed, the fresh web of material does not come into engagement with the cutting device, and only the old web of material is cut by the change of position of the cutting device.
In order to reliably prevent an unintentional cutting of the fresh web of material by the cutting device, a spacing element can be provided on the cutting device. By use of the spacing element, a defined minimum distance between the cutting device and the fresh web of material is assured.